Validation of asbestos exposure in mesothelioma cases clustered among residents near an asbestos cement pipe production factory and risk estimation of deaths due to mesothelioma.

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We obtained pleural tissue having mesothelioma, intact lung tissue or chest CT films from 72 mesothelioma cases or their families, who granted our interview study and gave a written informed consent. All cases were residents who had lived near an asbestos cement pipe production plant, Kubota. Pleural tissues were provided for re-examination for pathological diagnosis using an immunostaining assay, which consisted of both positive makers for mesothelioma and negative ones for lung cancer. Of 31 cases whose diagnosis was mesothelioma, only one case (3.0%) turned out to be a different disease by re-examination of the tissue. Three radiographic specialists agreed that all films fad findings consistent with those commonly observed in mesothelioma cases. They indicated an existence of pleural plaque in 23.7% of the study subjects. The number of asbestos bodies in the lung tissue was successfully counted in 12 subjects. Half of them showed the number which was much lower than that of workers exposed to asbestos occupationally but higher than in persons not exposed to asbestos of any kind. Asbestos fiber concentrations in the lung could be counted in five subjects. Fibers of crocidolite were found in all study subjects. However, we could not obtain definite conclusions because these subjects were likely to be exposed occupationally or domestically.These results suggest that misdiagnosis is much lower than we had imagined and neighborhood exposure to asbestos occurred among residents near the plant. Of 178 residents with asbestos-related diseases with whom we made an interview, 73, who lived in the area within 1, 500 meters from the plant, died from mesothelioma after Jan, 1, 1995 till the end of 2006. SMRs of mesothelioma increased significantly as high as 14 among men and 41 among women within 300 meters. A significant elevation of SMRs in women extended as far as 1, 500 meters way from the plant.